Several aspects of lipid-linked N-glycosidic glycoprotein biosynthesis in the yeast, Saccharomyces cerevisiae, will be studied. The structure of the oligosaccharide moiety of oligosaccharide-pyrophosphoryl-dolichol from this lower eucaryote will be examined to see whether it is similar to that from more complex animal cells. The role of glucose in the synthesis of oligosaccharide-lipid and subsequent transfer of the oligosaccharide to acceptor proteins will be evaluated. Once transferred to protein, the fate of oligosaccharide chains will be followed to determine whether a complex processing reaction, involving the excision of glucose and/or mannose residues, is carried out in yeast. Elongation of the inner core oligosaccharide to mature oligomannosyl chains, such as those of carboxypeptidase Y and external invertase which contain from 15 to over 50 residues, respectively, will also be investigated. The glycolipid:protein oligosaccharide transferase enzyme present in yeast rough endoplasmic reticulum will be purified, characterized, and used to study the mechanism of oligosaccharide transfer from the lipid-intermediates to protein acceptors.